1. Field of the Invention
The present invention relates to a receptacle connector serving as a female connector for an electrical connector configured to connect two circuit boards to each other. More specifically, the present invention relates to a receptacle connector having a crosstalk reduction structure, and to an electrical connector using the same.
2. Description of the Related Art
Heretofore, it is well-known to provide a receptacle connector serving as a female connector to a printed wiring board serving as a circuit board, and to electrically connect this printed wiring board to another printed wiring board serving as another circuit board through the receptacle connector. Such an electric connector at least including a receptacle connector has been disclosed in Japanese Patent Laid-Open No. 2007-149643, for example.
In the conventional receptacle connector, the following contact layout has been known in order to suppress crosstalk. Specifically, a coplanar structure is adopted as the contact layout, and ground contacts (G) are disposed such that the ground contacts sandwiches two signal line contacts (S) used for transmitting signals. That is, the contacts are laid out so as to form a G-S-S-G pattern.
However, along with speeding up of signal transmission in recent years, crosstalk between adjacent signal lines is becoming a serious problem. In particular, in high-speed transmission, it is necessary to suppress an amount of crosstalk to a very small level in a much higher frequency domain.
A layout structure generally used in connectors for high-speed transmission of differential signals is that the ground contacts are placed on both sides of two signal line contacts as in the G-S-S-G pattern as described above. Moreover, when a plurality of sets each consisting of two signal line contacts are adjacent to each other, the adjacent sets of two signal line contacts are separated from each other by only one common ground contact as in a G-S-S-G-S-S-G pattern.
In one instance of this the g round wires arranged on the printed wiring board are connected to one another by use of a ground common plane or the like inside the printed wiring board, for example, and are configured to have the same electric potential. However, in the case of a connector in which a plurality of contacts are connected to the printed wiring board through only both end sides of the plurality of contacts, the ground contacts are located at a distance from the ground common plane provided inside the print wiring board. As a result, the ground contacts of the connector have electric potentials different from each other, and have electric potentials also different from an electric potential of the ground wires on the printed wiring board. This degrades shielding effects of the ground contacts against high-frequency signals having frequency components of several gigahertz (GHz). As a consequence, there is a risk of causing a problem of increase in the crosstalk between two immediately-adjacent signal line contacts or between two adjacent signal line contacts located across a ground contact.
To solve this problem, the applicant has already proposed an invention in which a plurality of ground contacts arranged in a receptacle connector are coupled together by use of a common contact made of metal (see Japanese Patent Application No. 2010-019205 filed on Jan. 29, 2010). The present invention aims at a further improvement of this application.
An object of the present invention is to provide: a receptacle connector which achieves reduction in crosstalk between vertically or horizontally adjacent signal line contacts by equalizing electric potentials of ground contacts arranged across every two signal line contacts; and an electrical connector using the receptacle connector.